1. Field of the Invention
The present disclosure relates generally to linear actuators. More particularly, aspects of the disclosed embodiments relate to linear actuators that can be locked in position.
2. Description of Related Art
Conventional linear actuators have output rams that may be driven from a rotary source or with pneumatic or hydraulic pressure. The actuator may have a lock mechanism to retain the output in a fixed position. Known lock mechanisms, such as taught by Tootle in U.S. Pat. No. 4,463,661, engage an actuator synchronization system, and therefore provide only indirect locking to the output ram. Direct locking mechanisms that employ a linear actuator have been developed and typically include a multi-piece housing with increased size and mass. Such actuators include tine locks, an example of which is disclosed by Carlin in U.S. Pat. No. 5,267,760. While some tine lock arrangements may allow for a single-piece housing actuator, they have the disadvantage of using flexing lock element with consequential fatigue considerations. Locking Actuators can be operated by a rotary source rather than hydraulically or pneumatically. Present rotary source operated actuators, such as disclosed by Grimm in U.S. Pat. No. 4,603,594, have the disadvantage of requiring an electrically operated solenoid mechanism (or other mechanical input separate from the rotary source) to unlock the actuator lock before motion of the ram can commence. Ball Lock mechanisms such as taught by Sue in U.S. Pat. No. 4,703,683, Deutch in U.S. Pat. No. 4,240,332, and Della Rocca in U.S. Pat. No. 4,742,758 have the disadvantage of a low external load carrying capability of the ram because of the point contact stresses imposed on the lock balls. Linear motion lock sleeve and key arrangements, such as disclosed by Kopecek (the inventor of the present disclosure) in UK patent GB2435877, include a rotary-to-linear motion conversion mechanism for the lock sleeve and complexity associated therewith. Accordingly, it would be desirable to provide a linear actuator arrangement that overcomes at least some of the problems identified above.